This invention relates in general to devices for measuring characteristics of optical fiber. More particularly, the invention provides an optical fiber characteristic measuring device for automatically and successively measuring the characteristic data of a single mode optical fiber such as, for examples, structural parameters--outside diameter, core diameter, core eccentricity and non-circularity and non-structural parameters--spot size, cutoff wave length, and specific fraction difference.
Various parameters of a single mode optical fiber can be measured. These include geometrical structural parameters such as outside diameter, core diameter and core non-circularity, and non-structural parameters such as for examples, spot size, transmission loss, dispersion, backward scattering, cut off length, and specific refraction difference.
In general, in measuring geometrical structural parameters such as outside diameter, core diameter and core non-circularity, and the various other parameters, such as, spot size, cutoff wave length, and specific refraction difference, a portion of the optical fiber, approximately 1 to 2 m in length, is removed as a sample (i.e., the measurement with light transmitted through the entire optical fiber is not carried out because of the nature of the measurement) and is measured. The measured characteristics of the sample are assumed to be those of the entire optical fiber from which the sample was taken (for instance a bobbin of optical fiber).
Heretofore, for each of the above-described items of measurement, the ends of an optical fiber to be tested are set with respect to optical incident and emergent ends, such as the ends of optical fibers, which are connected to an ITV camera, a photo detector, a light source for a measuring instrument, and a light receiving unit, and are positioned. Under this condition, the measurement is carried out. Measurement is generally performed by a human operator stationed at each measuring instrument. Whenever a different parameter is to be measured, the optical fiber to be measured must be set again. This takes a considerable amount of time and labor. Furthermore, the optical fiber setting work cannot be carried out during the period of time that an optical fiber characteristic is being measured by a measuring instrument. This difficulty may be eliminated by alternately performing the optical fiber setting work and the measurement. However, even alternating, the number of items measured by one operation is only two. Thus, the conventional method of measuring the characteristics of a single mode optical fiber requires excessive labor and time. It is an extremely inefficient process.